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Richmond have been doing two things Squiggle particularly likes: Holding oppositions to low scores, and generating plenty of scoring shots.

The Tigers have been kicking plenty of behinds this season right from the start: In Round 1, they defeated Carlton by 4 goals and 14 behinds, while in losing to Adelaide the following round, they lost by 6 goals and 0 behinds.

On the surface, that’s a close-ish 26 point win followed by a heavier 36-point defeat; in terms of scoring shots, it’s a +16 smashing followed by a much closer -6.

Squiggle’s model considers the reality to be somewhere in between. As a result, it considers the Tigers’ only loss of the season so far to be a relatively close one, away interstate to a very good team – the kind of game that even a top team will often drop. The Tigers’ wins, on the other hand, have included some extraordinary smashings when viewed in terms of scoring shots.

Richmond’s opposition to date has mostly included mid- to upper-tier rated teams in Adelaide, Collingwood, Hawthorn, and Melbourne, yet across the season’s 6 rounds, the Tigers have averaged 50% more scoring shots. The result is a lot of Squiggle love for the yellow and black.

The Tigers have a monstrous gap over the rest of the comp, according to Squiggle modelling. This is the biggest gap between the best and second-best sides since the mid-2012 Hawks. pic.twitter.com/JbGufTJdtv

Most computer models of AFL have no awareness of who’s actually playing in either team. They rate the strength of competing clubs as an entity, rather than what they really are: a collection of moving parts, some of whom move a lot better than others.

Earlier this year, HPN, the artist formerly known as Hurling People Now, launched PERT, a tipping model that draws on the ratings of the actual players, as determined by the PAV system.

It’s early days, but PERT looks likely to add a fascinating new dimension to model-based tipping, and is definitely worth keeping an eye on.

Because PERT tips depend on the announced teams, they come out later in the week and can alter based on last-minute personnel changes.

I’m delighted to have HPN on board and PERT tips are now integrated into Squiggle dials and the leaderboard!

Squiggle would now project those 2nd-quarter scores of 2.9 (21) – 2.7 (19) out to 8.16 (64) – 10.15 (75)… which is more plausible. Although still not very close to the actual final scores of 13.17 (95) – 5.13 (43).

Pre-season Tracking: We had something resembling a normal preseason this year, so Squiggle is using those results in its calculations for the season ahead.

Round-based Sensitivity: Squiggle is now more sensitive in the early rounds and in finals, to better capture the important signalling of surprising results at these times. In particular, an unexpected Round 1 result can cause a team to move a very long way.

Goal-kicking Accuracy: As flagged last year, since goalkicking accuracy seems to be non-reproducible — teams that are highly accurate one week aren’t more likely to be highly accurate the next — Squiggle will interpret a scoreline like 13.20 as a team that was unlucky to not win by more, and thus will rate them more highly, while a scoreline like 12.3 will be interpreted as a team that got closer than they probably deserved.

Home Ground Advantage: Gone is the practice of assigning 12 points of home advantage to interstate hosts and ignoring everything else! Squiggle now calculates HGA based on relative ground & state familiarity: It scores each team on how many times they’ve played at the same venue and (less significantly) in the same state over recent years, and assigns HGA points based on how lopsided the numbers are. So at venues where both teams have played fairly often, ground familiarity is balanced and there’s not much HGA, if any. At venues where one teams plays a lot and the other team rarely even visits the state, HGA is high.

The main difference in practice is better modelling of Geelong in Melbourne, along with uncommon situations like Melbourne playing in the Northern Territory. For example, for the Round 1 Melbourne vs Geelong game at the MCG, under the old model Squiggle would give Melbourne 12 points of HGA, but under the new model, it’s only 2.5 points, due to the Cats’ fairly good familiarity with that ground.

Actually here are the current HGA values for all R1 matches:

Richmond +1.1 vs Carlton @ MCG

Essendon +7.9 vs Adelaide @ Docklands

St. Kilda +7.6 vs Brisbane @ Docklands

Port Adelaide +10.0 vs Fremantle @ Adelaide Oval

Gold Coast +10.3 vs North Melbourne @ Cazalys

Hawthorn -1.0 vs Collingwood @ MCG

GWS +9.0 vs Bulldogs @ UNSW Canberra

Melbourne +2.5 vs Geelong @ MCG

West Coast +10.9 vs Sydney @ Perth Stadium

Hawthorn are the only home team to have negative HGA. West Coast still get a bunch of HGA despite playing on a brand new ground due to the state-based numbers.

Home ground advantage is often overlooked, underrated, or just plain cocked up in fixture analysis. Which is strange, because it’s one of the most reliable predictors. We don’t know whether a team’s double-up opponents will become tougher or weaker in 2018, but we do know it’s always better to play interstate opponents at home.

In theory, all teams should face a balanced fixture, and travel to face interstate opponents the same number of times as they host them at home. But in practice, this doesn’t happen. Some teams enjoy home games against interstate opponents while staying local for their away games, and sometimes teams play “away” games at their home ground, with their opponents forced to travel to them.

This is home ground advantage fixture bias. The AFL does a pretty good job of managing it, but each year there are imbalances, with some sides coming out better than others, playing more games at favourable venues than unfavourable ones. While it’s not the only factor in fixture difficulty, I think it’s important enough to take a closer look. So in this post, I analyze every team’s fixture and discuss why it’s good, bad, or break-even.

Favourabity is the net total of points a team receives from home ground advantage during the season. Throughout 2018, Hawthorn will receive a net benefit of a little over five goals from home ground advantage, while the Suns will be penalized almost the same amount.

Favourability is calculated by classifying each game as one of three types:

Interstate advantage (+10): a team hosts an opponent who travels from interstate. This includes Geelong home games against Melbourne-based sides, given the Cats’ superb record there.

Local advantage (+1): a team hosts an opponent located in the same city.

Limited advantage (+5): a few specific cases: a Melbourne-based team hosting Geelong at the MCG or Docklands, Hawthorn or North Melbourne hosting a Melbourne-based team in Tasmania, and Melbourne hosting a Melbourne-based team in Darwin.

These numbers are, I think, generally accepted in AFL analytics. That is, it’s commonly agreed that interstate home advantage is worth somewhere in the realm of 10 points, while the advantage of playing a local team in your own city is almost negligible. If you want to adjust them a couple of points either way, though, I won’t quibble.

HAWTHORN

The Hawks travel to face interstate opponents four times, the fewest in the league, while interstate teams have to travel to face them six times, a league-high two-game discrepancy in their favour. On top of that, they play Geelong at home, which is worth +5, and they also have an “away” game against the Cats at the same venue. This effectively gives the Hawks 12 home games for the year, eight of which are against non-Melbourne sides.

That’s a remarkable number, only just short of the ten games that non-Victorian sides typically receive. In fact, it’s the same number as Gold Coast, who have to travel seven more times than the Hawks do to face interstate opponents.

And that’s not all: Hawthorn also take St. Kilda to Tasmania, which turns a +1 game into +5. The net result is a 32 point bonus over the course of the season.

Fremantle are the lucky recipient of an “away” game against Gold Coast in Perth due to the unavailability of Carrara due to Commonwealth Games renovations. This transforms the game from -10 to +10, giving the Dockers 11 games with interstate advantage in their favour and only nine against.

Richmond host interstate teams only four times, equal fewest in the league, while having to travel interstate themselves five times. But they more than make up for this by receiving two games against Geelong at the MCG, one of which is a nominal away game.

Geelong play just nine games at their true home and 13 games away, which is an enormous discrepancy. But since their Kardinia games are all rated +10 while their MCG and Docklands games are only -5, they come out even on balance.

This analysis may be too optimistic on Melbourne, even though they’re ranked fourth-last. That’s because the Demons host Adelaide and Fremantle in the Northern Territory, and these are classified as +10 games in Melbourne’s favour (hosting an interstate side at an alternative home ground), even though in practice, geography and history suggests it may not be deserved.

At least there’s a plausible explanation for Gold Coast’s terrible fixture: the unavailability of their home ground. What’s behind St. Kilda’s shafting, I can’t say. Firstly, the Saints host interstate sides only four times while traveling six times, which is a heavy imbalance in itself. But whereas Essendon are compensated for the same issue with an MCG game against the Cats, there’s no such balm for the Saints, who are bound for Kardinia Park. They also must travel to Tasmania to play Hawthorn, which turns a -1 game into -5.

The Suns immediately drop 20 points by playing a home game against Fremantle in Perth, which turns what should be a +10 game into -10. Then there’s a home game against Port Adelaide in China, knocking down a +10 game to +1 (nominal home team in neutral venue). It leaves them with 11 games where interstate advantage will work against them and only eight when it will be in their favour.

Over on Live Squiggle, we’re getting bullish on Port Adelaide and expecting the Crows to remain a force.

The Cats and Giants still have a bit to prove, though, after accumulating quite a few close wins in 2017, which is always suspicious. So while those two teams are contenders, they’re a tier below the top 4 prospects of Adelaide, Port, Richmond, and Sydney.

The Bombers are a good chance to make finals for the second year running, and the Saints lead a pack of clubs vying for a place likely to be vacated by West Coast.

In 2018, Squiggle is powered by a new algorithm! The main differences to last year’s model are:

Squiggle 2.0 is much more sensitive in the early rounds, so surprising results will cause a lot of chart movement. This better captures the substantial form change that can occur over an off-season.

Squiggle 2.0 considers goalkicking accuracy: It slightly discounts scores that were the result of unusually high accuracy (i.e. kicking many more goals than behinds), and is forgiving of scores that were the result of unusually low accuracy, as this tends to be non-reproducible.

We’ll see if this is enough to move up the Computer Model Leaderboard! Of course, it would be hard not to. 2017 was not a kind year.

I hope to have all the usual gang of Squiggle friends on board again, bringing you the best of online AFL analysis from around the web, and perhaps a couple of new additions.